RFR: 8311031: JTable header border vertical lines are not aligned with data grid lines [v2]

[Tejesh R]

On Tue, 4 Jul 2023 12:53:38 GMT, Alexey Ivanov <aivanov at openjdk.org> wrote:

>> Still I feel that would be blind comparison, since we won't be able to exactly test the fix.
>
> I strongly believe it should be an automated test. It may even be headless, if possible. There are a couple of examples which compare border rendering.
> 
> You don't need to store images, just count the number of pixels of a particular colour. If you detect an inconsistency, fail the test. You may need to tweak the width or height of columns and rows so that old method results in visible inconsistencies in rendering.

How will counting the number of pixels of a particular color help in validating the fix? I was planning to take a portion of image which includes header and 1st row and then check the column of vertical line from header to data, if all are same color then its a straight line, else fail the test... But I was not able to compare the data, some inconsistencies were there with rgb values.... Will try to work on that again......

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PR Review Comment: https://git.openjdk.org/jdk/pull/14766#discussion_r1252525241